While out walking the other day I was overcome by the smell of giant hogweed and was surprised how many flies were flying around it. This made me wonder why they were attracted to the smell.
Flowers use a combination of chemicals to emit a smell. Some flowers use smell to attract insects to pollinate while others use smell to repel insects. Flowers are used in cooking, essential oils and as air fresheners.
If you want to find out more then there is some great information below.
One of the first aspects of a flower you may notice is the beautiful smell they give off. These smells are not for us, however. The smells are used to attract insects to pollinate while also warning other insects away.
Most plants have a distinctive smell that allows you to identify them for one another. Some are pleasant to our noses such as the beautiful, sweet smell of roses or honeysuckle to the sharp, refreshing smell of mint. However, others such as hogweed are not pleasant at all.
Smells are made as a result of a combination of chemical substances. The plants synthesize the chemicals by using a lot of energy. Therefore it should be no surprise that flowers use their smell for many different things from defense to pollination. However, many plants are used by us in cooking due to their strong smells due to these chemicals.
There are a small number of plant families where a large proportion of their species have aromatic plants such as flowers, roots, stems or foliage, but there are many individual species that are aromatic.
Mint has several species in its family, and although they all smell much like we expect them to of mint, they all smell slightly different. All species of mint contain menthol, an ingredient which we use in many of our cold and cough medicines. Menthol is why all species of mint smell similar.
The differences between the different types of mint comes from the other substances and chemicals that they create, making some better for certain uses.
Daisies contain a number of different types in their family including many different scented plants. Pineapple weed smells similar to pineapples, while other members of the daisy family include chamomile, wormwood and mayweed.
The carrot family includes several different smelling plants as well. Wild carrot, hemlock, parsley and chervil are all part of the same family.
The scents of many flowers and plants are also used in essential oils. These are made up of the scented chemicals produced by plants. The oils are secreted by special cells in the petals, leaves or stems.
The oils either accumulate close to the surface, releasing their scent continuously in some plants, whereas others only release their scent if the plant is bruised or damaged.
Mint is a popular essential oil where the oil is close to the surface and is one of the reasons why the smell is so pungent and strong. Lavender and thyme oil evaporates slowly, leaving the smell hanging in the air for some time. Evaporation of the oil allows the plants to cool, helping the plant to avoid a loss of water from its leaves.
St Johns Wort has many oil glands in their leaves and the oil can be seen easily.
Wildwood garlic smell only when their leaves are bruised or crushed. If you have ever walked through a patch of wildwood garlic then you will know the smell they emit.
Although many plants smell nice and it is great that we can use them as essential oils, this is not the main reason for releasing these chemicals.
The smells act as chemical messages between themselves and insects or animals. The messages may be used to attract or repel certain species. The messages are even directed at certain species of animal.
Although we can smell plants and flowers, it is not very often that these messages are intended for us or other mammals. Some poisonous plants such as hemlock or hellebore use their smell to stop animals eating them.
Insects are the intended recipient of the smells from a plant or flower. Insects have an excellent sense of smell and can find the location of a flower from their smell. Insects are used for pollination and the smell allows the flower to reproduce which is their main aim.
The smell is effective over long distances and works much better in attracting insects than the color of the plant. The smell can be used not only to attract daytime insects but also to nocturnal insects, such as moths, allowing them to pollinate at night. The smell also allows plants that grow in shade to also attract insects.
Many plants do not rely on flowers at all as a means of attracting insects, relying on their scent to attract pollinators. Many plants that do not rely on flowers to attract insects are white
Butterflies and moths have such highly developed senses of smell that they can detect a single flower from more than 1km away. The increase in concentration as they get closer allows them to find the flower with ease.
Different plants use different combinations of chemicals depending on the type of pollinating insect that they are trying to attract. Flies are attracted to decaying flesh as larvae, and plants such as hogweed imitate this smell to attract them. Flies may use the plants to lay their eggs as they may still be convinced that what they have landed on is a dead animal.
While plants such as hogweed give off a decaying flesh smell, other plants give off a sickly sweet smell that attracts insects that are attracted to nectar. Bluebells, roses, and violets all attract butterflies that are attracted to the smell.
Caterpillars feed on plants that they find attractive. By feeding on them they store some of the plant’s scent in their bodies. Once they have gone through the pupa stage, metamorphizing into butterflies, they release some of these traces of scents which allows them to attract a mate.
Although many smells released attract different types of insects, some smells released warn insects away. Insects that can be harmful to the plant are often warned away by the smell, advising them to stay away from poisonous plants.
The poisons released act as a natural insecticides with the poisons being scented.
Wormwood can be used to keep flies out of a room and also to keep moths out of clothes due to their scent.
Some plant chemicals, such as pyrethrum is used in many commercial insecticides.
One of the ways that we use plants is as air fresheners. History has shown that we have used plants and herbs as air fresheners, strewn around houses on floors. Mints, rushes and sweet flag, one of the oldest known plants can all be used as air fresheners.
Many commercial air fresheners still use plants as their basis with essential oils being used. Pine has been used for more than a century, with pine cones being used historically as natural air fresheners, placed around the house and in clothes.
Many plants are used everyday for their aroma as herbs during cooking. Herbs were originally added to food to break up the monotony of eating the same dish every night, also improving food that may have gone slightly off.
Many herbs have been cultivated for centuries for use in food, spreading from herb gardens into the wild. Fennel, coriander and parsley are used everyday in cooking.